Fast LSX 92mm manifold
 

With a Ls6 headed and larger cam Ls1, is there enough of an advantage from the new Fast LSX 92mm manifold over the stock Ls6 manifold to warrant buying the Fast manifold? What is the largest throttle body I can put on my Ls6 manifold? My car is naturally aspirated and no nitrous.

Re: Fast LSX 92mm manifold
 

I don't know the answer, but I pulled the trigger to find out...however, my Fast 92mm is backorderd from Amazon right now, but my Nick Williams 92mm throttle body showed up this week!

I've got a stock internal LS6 crate motor with all the bolt-ons. The FAST 92mm has an advertised 15 HP gain over the LS6 intake, but from the resarch I've done, I think I can realistically expect a 10 rwhp gain. I plan to eventually go with a little bigger cam, so I'm thinking the FAST 92mm will be a good building block for the next round of internal mods...

Re: Fast LSX 92mm manifold
 

I gained 8rwhp going from a TPIS 90 intake w/90mmtb to the FAST 92 w/nw92tb so you'll probably see about 15rwhp going from a LS6 with gm 78mm ported tb. Now if you port the FAST 92 intake you can get another 5-10 rwhp, and more with a full port job if you're really good at it! I've since partially ported my FAST92 (just the last 3-4" before heads) and noticed a little more pep!

Re: Fast LSX 92mm manifold
 

Thanks guys. Do you know what the largest TB will work on the Ls6 manifold?

Re: Fast LSX 92mm manifold
 

I had a BBK 80mm on my LS6 intake at one point...it came with an adapter to fit the stock inlet on the manifold. I was advised to switch over to a stock ported TB when I got a dynotune, so I sold the BBK and had my stock TB ported.

Amazon canceled my order. They had the FAST 92mm listed for $762, so I ordered one. I got the email a couple of days ago that they can't get it and canceled my order. I was NOT happy. I found a sponsor that came pretty close to matching that price, so I have since re-ordered. I may look into sending it off and having it ported before I install it if it's really worth another 5-10 rwhp to have it ported!

Re: Fast LSX 92mm manifold
 

Thanks for sharing your experiance. It will help me make my decision.

Re: Fast LSX 92mm manifold
 

Seems like a lot of money for 15 hp. Just sayin'

Re: Fast LSX 92mm manifold
 

Thanks everyone for your input. I'm really torn here. CNC heads, new cam, Fast intake, and bigger throttle body starts to add up. I'm thinking for couple thousand more maybe moving up to an Ls3/l92 heads is money better spent.

Re: Fast LSX 92mm manifold
 

I know this thread is a couple months old but ..Sharing my experience the largest TB that would make any difference would be the diameter of the LS6 manifolds throat which is 80mm and I believe the stock TB is around 75. Going any larger serves nothing as the bottle neck becomes the throat. Going with an aftermarket TB would require a good tuner as then it becomes configuration issue with IAC counts, TPS, cold starts, etc. etc. The other reply mention going back to a ported stock which is another alternative. I had mine professionally tuned on the dyno and then more importantly running logs for cold starts, discovering/finding glitches in the OEM code, etc. etc. My two cents, which ever way you go, if you go larger get it professionally tuned. The LSX manifold gives a little benefit in the upper RPM range but you have to consider it that cost worth it. You call, but if you are on a budget like me, go with the LS6, aftermarket 80mm, cam, heads, exhaust, and GET IT TUNED.

Re: Fast LSX 92mm manifold
 

That's the plan. Thanks for your 2c's.